Abstract: A depressurization system includes a plurality of depressurization devices, each of which includes a cooling; and a compression device. The compression device includes a compression unit, which is provided with an AC electric motor, and supplies a compressed coolant to each cooling unit at a flow rate corresponding to a rotation speed of the AC electric motor. Each cooling unit supplements gas when adiabatically expanding the compressed coolant. The depressurization system also includes a temperature detection unit, which detects the temperature of each cooling unit, an inverter device, which is capable of changing a frequency of AC power supplies to the AC electric motor, and a frequency controller, which controls an output frequency of the inverter device.